Tip the apples into a preserving pan or large saucepan with 1.5 litres of water and the lemon peel. Bring to the boil over a medium heat, then reduce to a gentle simmer and cook for 30-40 mins, breaking the apples up with a spoon once softened a little, until the apples are pulpy. Spoon the apples and liquid into the bag of a jam strainer set over a large bowl and allow the juice to drop through (don’t be tempted to squeeze it through or it’ll go cloudy). Leave overnight if you can, or for at least a few hours.

Once the liquid has dripped through, weigh it to work out the amount of sugar needed. Once you have your weight of liquid, divide it by 4 then multiply that figure by 3 to work out three-quarters of the liquid’s weight. This is how much sugar you need (e.g. if you have 1 litre of liquid, you will need 750g sugar). Put the liquid, sugar and lemon juice into a large saucepan or preserving pan set over a medium heat and cook until the sugar has completely dissolved, without boiling. This should take around 5 mins. Bring to the boil and cook for around 10 mins, removing any scum that rises to the surface, until the mixture reaches 105C on a digital thermometer. You can also check it by putting a spoonful on an ice-cold plate – it should wrinkle when prodded. If it’s not set, keep cooking and checking every couple of minutes.

Pour into sterilised jars and seal before leaving to cool. Will keep, unopened, in a cool, dark place for three months.